The State thinks a blood result ends the argument. It doesn’t. Call (713) 664-4000 and we’ll show you why.
Jay Cohen is trained in forensic chromatography, the exact laboratory discipline Texas crime labs use to produce blood-alcohol results. We don’t stop at the one-page lab report with a number on it. We order the full litigation packet and read the raw chromatograms underneath it. The lab knows the difference between a lawyer who takes the report and a lawyer who checks the work.
Where blood cases crack
Before the lab ever sees it
Was the draw authorized, with real consent or a valid warrant? Was it done by qualified personnel with a non-alcohol swab? Was the tube the right type, unexpired, with the proper preservative and anticoagulant, inverted correctly, refrigerated properly? A blood sample is biological evidence. Store it wrong and it can literally ferment in the vial, creating alcohol that was never in your body.
Inside the lab
Headspace gas chromatography is a solid method run correctly, and full of failure points run carelessly: contaminated batches, co-eluting compounds misread as ethanol, calibration drift, uncertainty ranges the report conveniently omits. If your reported result is 0.09 with a realistic uncertainty band, the State’s “over the limit” story gets shaky fast.
Chain of custody
Every handoff between the draw, the fridge, the courier, and the lab bench must be documented. Gaps aren’t paperwork technicalities. They’re reasonable doubt.
In the courtroom
You have the right to confront the actual analyst who ran your sample, not a supervisor reading someone else’s file. Cross-examining a lab analyst is where the forensic training pays for itself.
The timing problem the State hopes you ignore
Blood is usually drawn an hour or more after the stop. The legal question is your alcohol level while driving. And the State’s attempt to project the number backward (“retrograde extrapolation”) rests on assumptions about absorption and elimination that often don’t survive an educated cross.
Watch: Blood draws, warrants and no-refusal weekends
When police can take your blood, when they need a warrant, and what a Texas “no refusal” weekend really means.
Can police take your blood without consent?
What to do during a “no refusal” weekend
Blood test FAQs
Is a blood test harder to beat than a breath test?
It can look that way, but it isn’t when you can read the data. Blood cases have more steps than breath cases (draw, storage, transport, analysis), and every step is a place the State can get it wrong.
Can they take my blood without my consent?
Generally they need a warrant. No-refusal weekends make warrants fast in Harris County, but fast warrants can be sloppy warrants. We review yours line by line.
The lab says my BAC was way over. Now what?
Now we get the litigation packet and find out what the number is actually built on. Come in for a free consult before you make any decisions: (713) 664-4000.
Make the lab show its work
If your case involves the breath machine instead, see how we challenge DWI breath tests, and protect your license at the ALR hearing. Talk to a Houston DWI lawyer who reads chromatograms: (713) 664-4000.
Reviewed by Jay Blass Cohen, founder of Blass Law PLLC, ACS-CHAL Forensic Lawyer-Scientist, certified Drug Recognition Expert, and SFST instructor, serving Houston since 2009. This article is general information, not legal advice for your situation. Prior results do not guarantee a similar outcome.